A system is being developed for clinical analysis using components that are significantly smaller than current analysis systems, and suitable for use in remote environments, such as space flight. Current systems for assaying medically-relevant parameters of blood typically require taking one or more venous blood samples, which are then analyzed in one or more large, specialized clinical autoanalyzer systems. Such systems, besides being bulky, generate significant volumes of medical waste, which must be treated as a hazardous material.
Moreover, current systems are often highly automated, and have dedicated staff to manage the flow of samples through the machine. Such systems are well adapted to hospitals and clinics. However, there are numerous situations which require more flexibility in a clinical analyzer, and which in particular have a low volume of sampling, requiring an analyzer which is suitable for intermittent use. Often, such requirements are presented by isolated populations or locations.
Such a flexible analyzer system is preferably highly automated in operation, so that it can be used without extensive training. Moreover, it should avoid or minimize the amount of waste generated, by minimizing the need for large samples and by flexibly running multiple assays on a single small sample (e.g., a finger prick vs. a sample from a vein). At the same time, it should have the ability to be used only intermittently, rather than daily or continuously as in most current analyzers. The system should also be flexible, to allow a wide variety of assays to be analyzed.
One important part of a system for accomplishing these objectives is a simple device and method for sample dilution, mixture of a sample with reagents, and delivery of the diluted sample to a flow cell for quantification of one or more parameters. Another important aspect of the system is the ability to work with small samples of blood or other bodily fluid, with sample volumes in the sub-milliliter range, for example 3 to 100 microliters. A related aspect of the system is the ability to perform continuous fluid flow at low differential pressures, to prevent leakage of components and for safety. Another aspect of the system is to provide an automated readout that is self-calibrated and that identifies the assay.
One route to these objectives is by size reduction of assay materials and systems. Several groups have shown that clinical analysis and similar laboratory procedures can be performed on devices that are greatly reduced in size compared to current clinical assay procedures. For example, White and Gilmanshin, in U.S. Pat. No. 7,595,160, use a nucleic-acid based probe of about 7.5-15 kilobases attached to antibodies, and so having an effective length of 10-20 microns for the DNA sequence. Doyle et al, in U.S. Pat. No. 7,709,544, describe a method of making small objects having different zones, by flowing parallel streams through a channel and polymerizing material contained in said streams. Masters, in U.S. Pat. No. 7,749,445, uses mixtures of sample materials with
These groups have demonstrated that clinical assays can be miniaturized and fabricated as nanostrips, and that nanostrips can be read by an optical system, for example by laser excitation of chromophores attached to reagents. In many cases, assays are evaluated by analysis of images of micro-strips. However, while the general feasibility of such a system has now been hypothesized for nearly a decade, there are still no actual systems of this sort on the market.
One of the limitations of prior microanalysis systems, using very small assay strips containing several zones, is the need to optically identify four different variables on each microchip passing through an analysis system. The first variable is the actual analytic result—for example, the amount of a particular protein or metabolite in a blood sample. These are the results actually delivered to the physician and the patient.
The second variable is a calibration procedure for the assay. It is highly desirable to have the assay nanostrip be self-calibrated, so that the reading of the analytic result is calibrated in real time-preferably on the same nanostrip, or in a reference nanostrip incubated in the same solution. This removes a variety of types of error that otherwise could occur.
The third variable is the identification of the assay. The nanostrips are platforms for assay, and are usable for many different assays. The system used to read the analytic result must also be able to issue a reliable output for identifying the assay being performed.
The fourth variable is the directionality of the nanostrip being analyzed. In the system of the invention, the nanostrip being read can enter the reading zone with either end leading.
In practice, an efficient implementation of the integration of these functions is required, so that the nanostrips of the invention are reliable and readily useable. Moreover, the system is preferably small enough and light enough to be portable, and simple enough to be used without lengthy training.